[time-nuts] Improving the stability of crystal oscillators
jmfranke at cox.net
Mon Oct 15 22:30:02 EDT 2007
This is something I have thought about but never did any experimentation.
With the low cost and increased availability of thermoelectric coolers, I am
interested in pursuing this concept. The unfortunate thing is that the
crystals are ground for 25C or the higher turnover temperature point. If
someone has a crystal that has drifted, it may be a good candidate for
experimentation. Another thought would be to let the crystal operate at its
natural frequency, divide it down to 1 or ten Hz and then phase lock a more
convenient crystal frequency to the low pulse rate. The idea is to save an
otherwise aged and well performing crystal.
----- Original Message -----
From: "Tom Van Baak" <tvb at LeapSecond.com>
To: "Discussion of precise time and frequency measurement"
<time-nuts at febo.com>
Sent: Monday, October 15, 2007 10:12 PM
Subject: Re: [time-nuts] Improving the stability of crystal oscillators
> As far as I can tell, temperature curve plots for quartz typically
> show both an upper and a lower turnover point (for example,
> see the pages below). Since the upper is well above maximum
> ambient, it makes sense that this point is used in O[ven]CXO.
> The question is -- does anyone know if the lower turnover point
> (LTP) is ever used? I ask because I heard that a quartz oscillator
> might have slightly better short-term stability at the LTP compared
> to the UTP. If so, this might argue for the extra trouble of using
> TEC for cooling in some low-noise applications.
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